Preparation of norbornene-type monomers is well known. Dicyclopentadiene can be made by dimerizing cyclopentadiene by the Diels-Alder reaction whereas dihydrodicyclopentadiene can be made by the Diels-Alder reaction of cyclopentadiene and cyclopentene. Norbornenes can also be prepared by the Diels-Alder reaction of cyclopentadiene with selected olefins to yield either norbornene or substituted norbornenes. Tetracyclododecene compounds are by-products formed from the Diels-Alder reaction of cyclopentadiene and norbornenes. Symmetrical and unsymmetrical trimers and tetramers of cyclopentadiene can likewise be prepared by the Diels-Alder reaction of cyclopentadiene or by heat-treating dicyclopentadiene.
Polymerization of norbornene-type monomers is performed by ring opening polymerization by means of a metathesis catalyst system which system includes a metathesis catalyst and a metathesis cocatalyst. The catalyst is generally selected from molybdenum, tungsten, and tantalum compounds whereas the cocatalyst is selected from organometallic compounds such as alkylaluminums and alkylaluminum halides.
U.S. Pat. No. 4,400,340 to Klosiewicz describes a tungsten-containing catalyst such as tungsten halide or tungsten oxyhalide. The catalyst is suspended in a solvent to prevent it from prepolymerizing a monomer to which is added an alcoholic or a phenolic compound to facilitate solubilization of the tungsten catalyst in the monomer and a Lewis base or a chelant to prevent premature polymerization of the solution of the tungsten compound and the monomer. Amount of the tungsten compound is 0.1 to 0.7 mole per liter of solvent. Weight ratio of the tungsten compound to the alcoholic or phenolic compound is 1:1 to 1:3, and amount of the Lewis base or chelant is 1 to 5 moles thereof per mole of the tungsten compound. Treatment of the tungsten compound should be carried out in the absence of moisture and air to prevent deactivation of the tungsten compound catalyst. The catalyst must be treated in the manner outlined above in order to render it soluble in the cycloolefin monomer. The cocatalyst in this patent is disclosed as being selected from tetrabutyltin and alkylaluminum compounds such as alkylaluminum dihalide or dialkylaluminum halide where the alkyl group contains 1 to 10 carbon atoms. The preferred alkyl group is ethyl with diethylaluminum chloride being the most preferred cocatalyst. These cocatalysts are sensitive to air and moisture but are readily soluble in the cycloolefin monomers.
U.S. Pat. No. 4,380,617 to Minchak et al discloses metathesis catalyst systems for polymerizing cycloolefins. The catalysts are defined as organoammonium isopolymolybdates and organoammonium isopolytungstates and these catalysts are soluble in cycloolefins and are insensitive to air and moisture. The cocatalysts in this patent are similar to the cocatalysts disclosed in U.S. Pat. No. 4,400,340 and are generally selected from organometallics, particularly alkylaluminum halides although in a less preferred embodiment, other metals can be used in place of aluminum such as lithium, magnesium, boron, lead, zinc, tin, silicon, and germanium. Also, metallic hydrides can be used in whole or in part for the organometallic cocatalysts. Alkylaluminum and the corresponding organometallic compounds can also be used as cocatalysts herein.
U.S. Pat. No. 4,426,502 discloses the use of alkoxyalkylaluminum halides or aryloxyalkylaluminum halides as cocatalysts in metathesis catalyst systems to polymerize cycloolefin monomers. These cocatalysts are disclosed as especially useful in conjunction with organoammonium isopolytungstate and isopolymolybdate catalysts in polymerization of cycloolefins or norbornene-type monomers. By modifying the alkylaluminum halide cocatalysts to alkoxy or aryloxy alkylaluminum halides, the reducing power of the cocatalysts is thus lowered to provide adequate pot life for mixing various ingredients at room temperature, and for work interruptions, before initiation of polymerization and subsequent rapid polymerization.